import java.util.Arrays;
import java.util.HashMap;
import java.util.Map;

public class test2 {
    public static void main(String[] args) {
        int[] nums = {2,7,11,15};
        int target = 9;
        System.out.println(Arrays.toString(twoSum(nums,target)));
        }

        public static int[] twoSum(int[] nums, int target) {
            Map<Integer,Integer> hashtable = new HashMap<Integer,Integer>();
            for(int i=0;i<nums.length;i++){
                if(hashtable.containsKey(target-nums[i])){
                    return new int[]{hashtable.get(target-nums[i]),i};
                }
                hashtable.put(nums[i],i);
            }
            return new int[0];
        }
    }

